Question

Help? Anyone have and idea?

Answer 1

$y=a\cdot b^x\quad,\quad b>0$

a)
$128=2 b^3\\ b^3=64\\ b=4\\\\ y=2\cdot4^x$


b)
$4=a\cdot b^0\\ 1=a\cdot b^2\\\\ a=4\\ 1=a\cdot b^2\\\\ 1=4\cdot b^2\\ b^2=\dfrac{1}{4}\\ b=\dfrac{1}{2} \vee b=-\dfrac{1}{2}\\ -\dfrac{1}{2}$